Condition detecting apparatus



Jan. 5, 1960 B. H. PINCKAERS 2,920,252

CONDITION DETECTING APPARATUS Filed Oct. 8, 1956 14 4 9 46 kl u 45 I6 L "r0 cmcun T0 l8 53 66 BE CONTROLLED 33 L32 es 9 I58 233 25 n 2|; I7 27 26 6029 LINE 3 TIME IN SECONDS IN V EN TOR. BALTHASAR H. PINCKAERS ATTORNEY 2,920,252 CONDITION DETECTING APPARATUS Balthasar H. Pinckaers, Hopkins, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application October 8, 1956, Serial No. 614,653 5 Claims. (Cl. 317--149) The present invention is concerned with an improved control apparatus and more particularly with an improved flame detector utilizing means to provide for safe operation of the flame detector.

The present invention can be used as a fire detector or as a flame detector to supervise the combustion established in a furnace. In many instances, particularly with large industrial burners, it is desirable to provide a flame detector which responds very quickly to the presence or absence of flame, thereby shutting the fuel valve before a large quantity of raw fuel is admitted to the fire box of the furnace. The electronic type flame detector provides the quick operation which is desirable. However, as with all electronic devices, the electronic flame detector is susceptible to malfunction which may cause the flame detector to falsely indicate that a flame is present.

It is the purpose of the present invention to provide an improved condition detecting apparatus which utilizes means to check the operation of the condition detecting apparatus during the operation thereof to insure that the condition detector is not falsely indicating the presence of a given condition.

It is a further object of the present invention to provide an improved flame detector wherein means are provided suchthat the absence of flame is periodically simulated to insure that the flame detector does not falsely indicate the presence of flame.

It is a further object of the present invention to provide an improved flame detector utilizing electron discharge devices wherein a flame sensing element causes an electron discharge device to assume a first state of conduction in the presence of flame, and employing a cycling timer which periodically causes the electron dis charge device to assume a second state of conduction, and having means responsive to both the presence of flame and the simulated absence of flame, both of which means must be actuated to indicate proper operation of the flame detector.

These and other objects of the present invention will be apparent to those skilled in the art upon reference to the following specification, claims and the drawings, of which Figure 1 is a schematic representation of the present invention, and

Figure 2 is a bar graph showing the time periods during which the switches of the motor driven timer of Figure l are, opened and closed.

Referring specifically to Figure 1, the reference numeral designates a fuel burner. Associated in the proximity of this fuel burner is a flame sensing means 11 in the form of a photoemissive cell having an anode 12 and a cathode 13. The particular modification of Figure 1 is a flame detector wherein the flame sensor 11 is associated with the burner 10 and supervises the established flame at the fuel burner 10. However, it is within the teachings of the present invention to utilize a flame sensor such as ,ll to supervise a particular area and protect this area against the establishment of a fire.

United States Patent 0 The photoelectric cell 11 is connected by means of electrical conductors 14 and 15 to the remaining portion of the flame detector. Electrical energy is supplied to the flame detector by means of a transformer 16 having a primary winding 17 and having secondary windings 18, 19 and 20. The transformer primary winding 17 is connected by means of power line conductors 21 and 22 to a source of alternating voltage, not shown.

The reference numerals 23 and 24 designate first and second electron discharge devices respectively. The first electron discharge device includes an anode 25, a control electrode 26, and a cathode 27. The second electron discharge device includes an anode 28, a control electrode 29, and a cathode 30.

The operating voltage for the first electron discharge device 23 is derived from the secondary winding 19. The cathode 27 of electron discharge device 23 is connected by means of conductor 31 to the lower terminal of the secondary winding 19 while the anode 25 of this electron discharge device is connected through a load impedance including resistor 32 and capacitor 33 to the upper terminal of secondary winding 19. The input circuit to the network comprising the electron discharge devices 23 and 24 includes the capacitor 34 which is arranged to be charged in accordance with the condition to which the photocell 11 is subjected, as will be described.

The input circuit of electron discharge device 24, that is the circuit between the control electrode 29 and the cathode 30, includes the load impedance of electron discharge device 23 and this electrical circuit is so arranged that the voltage developed across capacitor 33 when electron discharge device 23 is in a conducting state biases electron discharge device 24 to be nonconducting.

The output circuit of the network comprising electron discharge devices 23 and 24, that is the anode cathode circuit of discharge device 24, includes a first relay 35 and a second relay 36. Relay 35 includes a winding 37 which is shunted by a capacitor 38, and includes a movable switch blade 39 and a contact 40. The relay 35 is shown in the state wherein its winding 37 is energized due to electron discharge device 24 being in its nonconducting state, as it normally is with the flame not present at the burner unit 10. In this condition, the movable switch blade 39 engages contact 40. Upon deenergizetion of relay winding 37, movable switch blade 39 is biased, by means not shown, to disengage contact 40.

Relay 36 includes a winding 41 which is shunted by a capacitor 42 and includes a movable switch blade 43 and a contact 44. Relay 36 is shown in the state wherein its winding 41 is deenergized, as it normally is when no flame is present at the burner unit 10. Upon energization of the winding 41, movable switch blade 43 moves into engagement with contact 44 and completes a circuit to conductors 45 and 46. The switching action of relay 36 may provide a variety of effects and for purposes of simplicity, a single switch 4344 has been shown which is adapted to be connected to a circuit to be controlled in accordance with the presence or absence of flame at the burner unit 10.

The input to the network comprising discharge devices 23 and 24 and the manner in which the relays 35 and 36 are connected to the output of this network is supervised by a motor driven timer designated within the broken lines 47. This motor driven timer includes a motor or actuator 48 which is at all times connected to the power line conductors 21 and 22 by means of conductors 49 and 50. This motor driven timer includes three switches,

designated as S1, a second of which a first of which is is designated as S2, S3. The bar graph bar portion thereof the relative time periods during which the switches are closed. The motor driven timer 47 and a third of which is designated as retreated Jan. 5, 1960,

of Figure 2 shows by means of the for the first portion of the cycle and closed for the second portion of the cycle.

Operation The apparatus of Figure l is shown in its standby condition. In this condition, the power line conductors 21' and 22 are connected to the source of alternating voltage tothereby provide a voltage in the secondary windings 18', 1% and 2h. The secondary winding 20 is connected,' by conductors not shown, to energize the filament windings of the electron discharge devices 23 and 24 and to thereby place these electron discharge devices in an operatingcondition. Furthermore, the secondary winding 18 in cooperation wit a the rectifiers 5i and 52 establishes. a direct current voltage across capacitor 53 which is'of the polarity indicated in Figure 1. The actuator d3 of motor driven timer 47 is energized and continues to cycle its switches in the manner indicated in Figure 2.

Furthermore, the winding 37 of relay 35 is energized whereas the winding 41 of winding 36 is deenergized.

The specific manner in which the apparatus of Figure l operates will now be described. As has been pointed out, the photoelectric cell ll is of the photoemissive type. in other words, this photoelectric cell is essentially a rectifier, and it is well to point out that photoelectric cell 11 may be replaced by the well known flame'rod, which likewise produces a rectifying effect when a flame is present at the burner unit ltl'. Electric power is supplied to the photocell ill by means of a circuit which can be traced from the upper terminal of transformer secondary winding 19 through a capacitor 54, conductor 15, anode 12 and cathode 13 of photocell 11, and conductor M to the lower terminal of secondary winding 19. When a flame is present at the burner unit it), the capacitor 54 is charged such that its right hand terminal is negative with respect to its left hand terminal. When such a voltage exists across capacitor 54, this voltage is applied to the capacitor 34 through resistors 55 and 56.

This voltage developed across capacitor 34 is such that its, upper plate is negative with respect to its lower plate. The upper plate of capacitor 34 is connected by means of conductor 57 to the control electrode 26 of discharge device 23 whereas the lower plate of the capacitor is connected by means of conductor 31 to the cathode of this discharge device. Therefore, when a voltage exists across capacitor 34 due to the presence of flame at the burner this voltage biases electron discharge device 23 to the cutoff or nonconducting condition.

.Since a flame does not now exist at the burner unit Ill, the above described voltage does not at this time exist across capacitor 34 and discharge device 23 is in its conducting state. However, if it were assumed for the moment that. a flame does in fact exist at the burner unit 10, a voltage would still not be developed across capacitor 34 due to the action of the switch S1 of the motor driven timer 47. It can be seen that switch S1 is connected in parallel with capacitor 34 and during the first portion of the cycle of the motor driven timer during which S1 is closed no voltage can be developed across capacitor 34, thereby insuring that electron discharge device 23 will always be in its conducting state during the first portion of the cycle irrespective of whether or not the flame is present at the, burner unit 10.

It is well to note at this point that the second portion of the cycle of the motor driven timer 47 wherein the switch S1 is in the open condition provides the time periodv during which the photoelectric cell 11 and I of ilarneat the burner unit iii. In other Words, if a flame is present at the burner unit 1% during the second portion of the cycle of the motor driven timer, a voltage is developed across capacitor 34 and electron discharge device 23 is rendered nonconductive. However, in the absence of flame at the burner unit it), no voltage is developed across the capacitor and electron discharge device 23 remains in its conducting state in both the first and second portion of the cycle of the motor driven timer 47.

This latter described alternative is the condition in which the apparatus of Figure l is operating. Namely, there is no fianme at the burner unit 1% and electron discharge device 23 remains in its conducting state during both the first and the second portion of the motor driven timer. In this condition, the current flow for electron discharge device 23 can be traced from the lower terminal of secondary winding 12 through conductor 31, cath-' ode 27 and anode 25 of discharge device 23, parallel connected resistor 52v and capacitor 33 and conductor 57 33 and this charge is maintained during the half cycle in which discharge device 23' is nonconducting.

The current flow through the load impedance of discharge device 23 causes capacitor 33 to be charged suchthat its lower plate is negative with respect to its upper plate. The lower plate of capacitor 33 is connected by means of conductors 59 and 66 to the control electrode 29 of discharge device 24 whereas the cathode 30 of this discharge device is connected by means of a con ductor 61 to the upper terminal of capacitor 33. This voltage across capacitors 33 biases electron discharge device 24 to be substantially nonconducting, or cutofl. In other words, the impedance of electron discharge de--v vice 24 from its anode 28 to its cathode 30 is now relatively high.

In the condition of the apparatus as shown in Figure l, the switch S2 is now in its closed condition while the switch S3 'is in its open condition. With switch S2 in its closed condition the relay winding 37 of relay 35 is now connected in parallel with the anode and cathode of discharge device 24. This can be seen by tracing a circuit from the cathode 36 through resistor 62, relay winding 37, conductor 63, timer switch S2, and conductor 64 to the anode 28 of discharge device 24. Since the impedance of discharge device 24 is now relatively high an energizing circuit can be traced from the positive power supply terminal 65 through conductor 66, resister 67, conductor 64, timer switch S2, conductor 63, relay winding 37, resistor 62, and conductor 61 to the negative power supply terminal 68. This above tracedcircuit is the energizing circuit for the relay winding 37, and causes movable switch blade 39 to' engage contact 40, as shown in Figure 1.

As has been mentioned, during the first portion of the cycle of the motor driven timer 47 in which the switches- S1 and S2 are closed and in which the switch S3 is open, the switch S1 simulates the absence of flame at the burner unit 10 by'shorting capacitor 34 and insuring that no voltage can be applied to control electrode 26 and cathode 27 of electron discharge device 23 This in turn insures that electron discharge device 24 is in its non-conducting state and that relay winding 37 is then energized, during the first portion of the'cycle of the motor driven timer 47. The energizing current which flows, in the above traced circuit charges capacitor 38' and insures that the winding 37 will remain energized during the second portion of the cycle of the motor driven timer 47 during which the apparatus is, rendered operative to sense the presence of flame at the burner unit 10. However, if it is assumed, for the moment that.

From this above traced circuit it. can be seen that a malfunction develops in the apparatus of Figure 1 such that the apparatus can not detect the simulated absence of flame, for example assume that discharge device 23 becomes inoperative due to an open circuit in its filament, then the voltage developed across capacitor 33is not present to bias discharge device 24 to its nonconductive state. Therefore, the impedance between the anode andcathode of discharge device 24 is relatively low and the winding 37 of relay 35 is substantially shorted, thereby preventing winding 37 from being energized and insuring that the movable switch blade 39 remains in its position where it disengages contact 40. This is a protective feature of the apparatus of Figure 1 and insures that the relay 36 can not be energized.

Considering now the second portion of the cycle of the motor driven timer 47, and assuming there is no malfunction as above described, the switches S1 and S2 now open and' the switch S3 closes. With the switch S1 open, the capacitor 34 may now be charged if photocell 11 is subjected to a flame. The opening of switch S2 opens the energizing circuit for the winding 37 of relay 35. However, as above described the relay winding remains energized due to charge on capacitor 38. The closing of timer contact S3 completes a circuit which is effective to energize the winding 41 of relay 36 in the event that photoelectric cell 11 detects flame. Assume for the moment that photoelectric cell 11 does in fact detect a flame at the burner unit 10. A voltage is now developed across capacitor 34, as above described, and electron discharge device 23 is biased to its nonconducting state. The voltage across capacitor 33 no longer exists and the discharge device 24 is therefore rendered conductive. An energizing circuit for the winding 41 of relay 36 cannow be traced from the upper terminal of secondary winding 18 through rectifier 51, conductors 69 and 70, relay winding 41, conductor 71, contact 40 and switch blade 39 of relay 35, conductor 72, timer contact S3, conductors 73 and 64, anode 28 and cathode 30 of discharge device 24, and conductors 61 and 57 to the lower terminal of secondary winding 18. It can be seen that there are essentially three switches in this above traced circuit. The first of these is the switch 39-40 which is closed only when relay winding 37 is energized. The second of these switches is timer switch S3 which is closed only during the second portion of the cycle of the motor driven timer. The third of the switches is discharge device 24 and this switch, recognizing that when discharge device 24 is conducting it can be considered to act as a switch, is closed only when no voltage exists across capacitor 33 which in turn depends upon discharge device 23 being biased to its noncondncting state.

Therefore, it can be seen that the winding of relay 36 is energized when photocell l1 detects a flame during the second portion of the cycle of the motor driven timer and thatthis relay winding remains deenergized in the event that photoelectric cell 11 detects the absence of flame during this portion of the cycle. The capacitor 42,.is provided in parallel with the winding 41 of relay 36 to insure that the winding 41 will remain energized during the first portion of the cycle of the motor driven timer during which the timer switch S3 is open to break the above traced energizing circuit,

In a particular modification of the present invention the components of the apparatus had values as indicated in the following table.

Discharge devices 23 and 24 12SN7. Transformer Winding 18 370 volts. Transformer Winding 19 200 volts. Resistor 32 22,000 ohms. Resistor 55 22 megohms. Resistor 56 22 megohms. Resistor 62 25.000 ohms. Resistor 67 39,000 ohms. Resistor 74 120,000 ohms.

Capacitor 53 4O microfarads.

The above component values are intended to be a representative modification of the present invention and in no way limit the scope of the present invention.

From the above description it can be seen that I have provided an improved condition detecting apparatus and in particular an improved flame detector which periodically checks itself against malfunction.

While the preferred modification has been explained in connection with a flame detector it is intended that the scope of the present invention be limited solely by the scope of the appended claims.

I claim as my invention:

1. Flame detector comprising; an electronic network having an input and having an output stage including an electron discharge device having a pair of main electrodes, flame sensing means, means including said flame sensing means connected to the input of said network to apply a signal thereto in accordance with the condition to which said flame sensing means is subjected to render said discharge device non-conductive in the absence of flame and conductive in the presence of flame, a first relay having a winding and a switch, a second relay having a winding, a timer having a plurality of switches actuated in a predetermined reoccurring cycle, circuit means including a first of said timer switches connected to said network in a manner to render said discharge device insensitive to a signal from said flame sensing means during a first portion of the cycle of said timer, circuit means including a second of said timer switches connecting the winding of said first relay in parallel with the main electrodes of said electron discharge device to a source of voltage to energize the winding of said first relay when said electron discharge device is non-conductive during the first portion of the cycle of said timer, and circuit means including a third switch of said timer and said first relay switch connecting said second relay winding in series with the main electrodes of said electron discharge device to a source of voltage to energize the winding of said second relay upon said electron discharge device being conductive during the second portion of the cycle of said timer.

2. A flame detector comprising a first electron discharge device having a control electrode and an anode and cathode, a load impedance, circuit means connecting the anode and cathode of said first electron discharge device in series with said load impedance to a source of voltage, flame sensing means, means including said flame sensing means connected to the cathode and control electrode of said first electron discharge device and arranged to bias said first electron discharge device substantially .to cutofl upon said flame sensing means being subjected to the presence of flame, a second electron discharge device having a control electrode and an anode and cathode, circuit means connecting the control electrode and cathode of said second electron discharge device to said load impedance in a manner to bias said second electron discharge device to cutoff upon said first electron discharge device being rendered conductive, a continuously energized timer having a first, a second and a third switch which are controlled in acyclic manner, said first and second switches being closed and said third switch being open in a first portion of the cycle of said timer and said third switch being closed and said first and second switches being open in the second portion of the cycle of said timer, circuit means including said first timer switch shorting the control electrode and cathode of said first electron discharge device during the first portion of the cycle of said timer, a first relay having an actuator and including means to delay the dropout timing of said first relay and having a relay switch which is closed upon said actuator being energized, circuit means connecting the anode and cathode of said second electron discharge device to a source of voltage, circuit means including the second switch of said timer when closed connecting the actuator of said first relay to the anode and cathode of said second electron discharge device such that said first relay actuator is energized so long as the second, electron discharge device in non-conductive during the first portion of the cycle of said timer, a-second relay having an actuator, and circuit means including the switch of said first relay and said third timer switch connecting said second relay actuator in series with the anode and cathode of said second electron discharge device to a source of voltage to thereby energize said second relay winding upon said second electron dis charge device being rendered conductive due to said flame sensor being subject to a flame during the second portion of the cycle of said timer.

3'. A flame detector comprising; a first electron discharge device having a control electrode and an anode and cathode, impedance means, circuit means connecting said anode and cathode through said impedance means to a source of voltage, flame sensing means, circuit means connecting said flame sensing means to the control electrode of said'first discharge device to cause said first discharge, device to be conductive in the absence of flame,

discharge device is conductive, a first relay having a winding, 21 second relay having a winding, a timer having an actuator and a first, a second and a third switch controlled in a cyclic manner, circuit means connecting said timer actuator to a source of Voltage, said first and second switches being closed and said third switch being open for the first portion of the timer cycle and said thirdswitch being closed and said first and second switches being open for the second portion of the timer cycle, circuit means including said first timer switch connected to said first discharge deviceto simulate the absence of flame when said first switch is closed to thereby render said first discharge device conductive, further circuit means including said second timer switch connecting the winding of said, first relay to the anode and cathode of said second discharge device and to a source ofvoltage to energize said first relay winding during the first portion of the timer cycle when said second discharge device is non-conductive, and further circuit means controlled by said third timer switch connecting said second relay Winding in series with the anode and cathode of said second discharge device and a source ofvoltage to render said second relay winding energized when said second discharge device is conductive.

4. A condition detecting device comprising; condition sensing means, an electron discharge device having a cathode, an anode and a control electrode, circuit means 8-: connectingsaid condition. sensing means to the control electrode of said discharge device to control the state of conduction of said discharge device in accordance with" the condition to which said condition sensing means is subjected, first voltage responsive means having an actuator and a normally open switch controlled thereby, second voltage responsive means having an actuator, cycling switch means, means connected tosaid condition sensing means and controlled by said cycling switch means to periodically simulate a condition causing said discharge device to be non-conductive, and further means controlled by said cycling switch means to first connect the actuator of said first voltage responsive means to the cathode and anode of said' discharge device and to a source of voltage during that portion of the cycle during which said condition is simulated to thereby cause the switch of said first voltage responsive means to assume a closed'position upon said discharge device responding to the simulated condition, and to then connect the actuator of said second voltage responsive means and the switch of said first voltage responsive means in a series circuit with the cathode and anode of said discharge device toa source of voltage during that portion of the cycle during which said condition is not simulated.

5. An electronic condition detector comprising a network having aninput and an output, condition sensing means connected to said input and arranged to supply a control voltage thereto when said condition sensing means is subjected to a given condition, timing means having switch means connected to the input of said network and arranged to periodically simulate the absence of the given condition at a given rate, first relay means having a long drop-out time and having an actuator with switch means control-led thereby, the drop out timing of: said first relay means being such that when the actuator of said first relay means is periodically energized at said given rate the switch means of said first relay means is continuously maintained in an energized position, circuit means connecting said first relay actuator to the output of said network in such a manner that said first relay actuator is periodically energized at said given rate during said simulated absenceof the given condition, second rela'y means having an actuator, and circuit means in cluding the switch means of said first relay means when in said energized position connecting the actuator of said second relay means to the output of said network, in a manner to energize the actuator of said second relay means when the control voltage is applied to the input of said network.

References Cited in the file of this patent UNITED STATES PATENTS Consoliver et al. Feb. 25, 1958' 

